The invention concerns a device for generating a dry, cold air flow for treatment of rheumatic diseases.
Cold therapy for treatment of rheumatic diseases was developed some years ago in Japan and is increasingly gaining recognition. Both whole body therapy and local therapy has been applied. In whole body therapy, the patient must remain in a severly chilled room for a specific period of time. In local therapy, a cold air flow is directed onto the diseased body portion. The invention concerns a device for local therapy.
The cold air flow for local therapy must be dry and free of ice. Since the air is cooled to approximately -150.degree. C., it is by nature dry, but the ice particles removed from the air by freezing must be prevented from impacting on the body surface. This would cause cold damages at least in the form of micronecroses.
From the Japanese disclosure document for design registration, No. 30 189/80 (Application No. 114 029/78), a device is known for generating a dry, cold air flow for treatment of rheumatic diseases, which fulfills the above-mentioned requirements. In this device, the air flow generated by means of a blower is led through an air cooler, in which it is cooled to the required low temperature. This air cooler is a heat exchanger with cooling hoses, in which liquid nitrogen is being evaporated. The moisture is frozen out at these cooling hoses. The dry cold air is removed from the air cooler through an insulated hose and fed to the treatment location.
Although this device fulfills its purpose in a satisfactory manner, it has some disadvantages, particularly in respect to economy. Thus, the investment costs are relatively high, since the heat exchanger for the air cooling is expensive. The heat exchanger must be set up outside of the treatment rooms. For this reason, long feed lines are required. The long hose line for the cold air is also expensive, due to the cost of the insulation. When the device is started up, it is necessary to first cool the heat exchanger with its great mass as well as the hose lines, before it is possible to give the patient the cold treatment. The start-up times are thus considerable. The loss of cooling agent per treatment is correspondingly great. If the device is being used for a longer period of time without interruption, which is frequently the case in the practice, the moisture frozen out of the air may ice the surfaces of the heat exchanger and cause a failure of the device. This can be prevented only if the operation of the equipment is set for regular intervals to thaw off the accumulated moisture.